1. Field of the Invention
The present invention relates to a power source apparatus used primarily as the power source for a motor that drives a vehicle such as a hybrid or electric vehicle, and to a vehicle with the power source apparatus installed on-board.
2. Description of the Related Art
Vehicles such as electric vehicles (EVs, electric cars, electric automobiles) driven by an electric motor, or hybrid vehicles (HVs, hybrid electric vehicles, HEVs, hybrid cars) driven by both an electric motor and an engine, carry a high capacity power source apparatus on-board to supply power to the driving motor. To attain an output that can drive a vehicle with an electric motor, the power source apparatus has numerous battery cells connected in series to increase the output voltage. During inspection and maintenance, or when the power source apparatus is not installed in the vehicle, exposure of high-voltage areas of the power source apparatus such as high-voltage output terminals presents a safety hazard. To avoid this safety hazard, a battery system has been developed with a service plug connected in series with the batteries. In this battery system, output voltage can be shut-off by removing the service plug. Since the service plug can be removed to shut-off output voltage during maintenance operations, those operations can be performed safely.
The service plug is connected in a removable manner in a socket disposed on the case of the power source apparatus. Since the service plug is connected in series with the batteries and subject to high-current flow, arching can occur if the service plug is removed from the socket when high-current is flowing. To prevent the spread of flames from an arching service plug, a service plug has been developed housing a gas-jet source (such as an air-bag inflator) to eject a nonflammable gas into the service plug.
Refer to Japanese Laid-Open Patent Publication 2004-7920.
The service plug described above houses a gas-jet source that delivers a nonflammable gas and a controlling device that determines if conditions warrant gas delivery. The controlling device detects the conditions for gas introduction and injects nonflammable gas from the gas-jet source into the socket. In an emergency situation such as an automobile accident when the amount of acceleration (deceleration or impact) input from an accelerometer exceeds a preset value (such as the value for air-bag activation), the controlling device determines that the conditions for gas injection are satisfied when the speed sensor indicates that the vehicle is stopped, and the lever-switch that detects service plug removal is in the OFF state indicating service plug removal. Under those conditions, the controlling device activates the gas-jet source and injects a nonflammable gas such as nitrogen into the socket.
In addition to having an extremely complex structure, the service plug described above has flame-retarding gas introduced in situations assumed by detecting specific conditions. Consequently, depending on the conditions, the spread of flames may not be effectively prevented. In particular, since the service plug inserts into the socket to connect the batteries through a pair of plug-side connecting terminals (blades) that connect with receiving socket-side connecting terminals (recepticles), high current flow can heat the connecting regions to abnormally high temperatures when contact resistance is significant. The contact resistance of the connecting regions can increase over time. The contact resistance of the connecting regions between lead-wires connected to the batteries and the socket-side connecting terminals, and the contact resistance of the connecting regions between the plug-side and socket-side connecting terminals can become large. Lead-wires connected to the batteries are joined to metal socket-side connecting terminals by crimping, or the ends of the lead-wires are connected to crimped terminals that are screw-attached to the socket-side connecting terminals. Plug-side connecting terminals resiliently press into the socket-side connecting terminals for connection. With this connecting region configuration, contact resistance increase due to vibration and aging cannot be neglected. When contact resistance increases, the connecting regions over-heat due to Joule-heating, which is proportional to the square of the current times the contact resistance. This leads to detrimental effects including the possibility of smoke and flame generation and the associated spread of fire to ignite other regions. In particular, since current flow in a vehicle power source apparatus is greater than or on the order of 100 A, Joule-heating proportional to the square of the current becomes extremely high even with a small increase in contact resistance and this can result in detrimental effects such as fire ignition.
The present invention was developed considering this background. Thus, it is a primary object of the present invention to provide a power source apparatus and vehicle carrying the power source apparatus that can demonstrably improve reliability by effectively preventing the spread of detrimental effects due to over-heating of the connecting regions between the service plug and socket while employing an extremely simple structure.